[Xen-changelog] [xen staging-4.9] x86/pv: Introduce and use x86emul_read_dr()

[patchbot@xxxxxxx]

commit 52fa2f7d62090767b799d287c48a2146358a3953
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Fri May 18 11:54:05 2018 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri May 18 11:54:05 2018 +0200

    x86/pv: Introduce and use x86emul_read_dr()
    
    do_get_debugreg() has several bugs:
    
     * The %cr4.de condition is inverted.  %dr4/5 should be accessible only when
       %cr4.de is disabled.
     * When %cr4.de is disabled, emulation should yield #UD rather than complete
       with zero.
     * Using -EINVAL for errors is a broken ABI, as it overlaps with valid 
values
       near the top of the address space.
    
    Introduce a common x86emul_read_dr() handler (as we will eventually want to
    add HVM support) which separates its success/failure indication from the 
data
    value, and have do_get_debugreg() call into the handler.
    
    The ABI of do_get_debugreg() remains broken, but switches from -EINVAL to
    -ENODEV for compatibility with the changes in the following patch.
    
    Take the opportunity to add a missing local variable block to x86_emulate.c
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
    master commit: 881f8dc4314809293efc6f66f9af49734994bf0e
    master date: 2018-04-17 15:12:36 +0100
---
 xen/arch/x86/traps.c                   | 33 +++--------------------
 xen/arch/x86/x86_emulate.c             | 49 ++++++++++++++++++++++++++++++++++
 xen/arch/x86/x86_emulate/x86_emulate.h |  3 +++
 3 files changed, 56 insertions(+), 29 deletions(-)

diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 938f7aeb85..1f3881e5b3 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -2494,19 +2494,6 @@ static int priv_op_write_cr(unsigned int reg, unsigned 
long val,
     return X86EMUL_UNHANDLEABLE;
 }
 
-static int priv_op_read_dr(unsigned int reg, unsigned long *val,
-                           struct x86_emulate_ctxt *ctxt)
-{
-    unsigned long res = do_get_debugreg(reg);
-
-    if ( IS_ERR_VALUE(res) )
-        return X86EMUL_UNHANDLEABLE;
-
-    *val = res;
-
-    return X86EMUL_OKAY;
-}
-
 static int priv_op_write_dr(unsigned int reg, unsigned long val,
                             struct x86_emulate_ctxt *ctxt)
 {
@@ -3023,7 +3010,7 @@ static const struct x86_emulate_ops priv_op_ops = {
     .read_segment        = priv_op_read_segment,
     .read_cr             = priv_op_read_cr,
     .write_cr            = priv_op_write_cr,
-    .read_dr             = priv_op_read_dr,
+    .read_dr             = x86emul_read_dr,
     .write_dr            = priv_op_write_dr,
     .read_msr            = priv_op_read_msr,
     .write_msr           = priv_op_write_msr,
@@ -4300,22 +4287,10 @@ long do_set_debugreg(int reg, unsigned long value)
 
 unsigned long do_get_debugreg(int reg)
 {
-    struct vcpu *curr = current;
-
-    switch ( reg )
-    {
-    case 0 ... 3:
-    case 6:
-        return curr->arch.debugreg[reg];
-    case 7:
-        return (curr->arch.debugreg[7] |
-                curr->arch.debugreg[5]);
-    case 4 ... 5:
-        return ((curr->arch.pv_vcpu.ctrlreg[4] & X86_CR4_DE) ?
-                curr->arch.debugreg[reg + 2] : 0);
-    }
+    unsigned long val;
+    int res = x86emul_read_dr(reg, &val, NULL);
 
-    return -EINVAL;
+    return res == X86EMUL_OKAY ? val : -ENODEV;
 }
 
 void asm_domain_crash_synchronous(unsigned long addr)
diff --git a/xen/arch/x86/x86_emulate.c b/xen/arch/x86/x86_emulate.c
index c7ba221d11..d3155a09d5 100644
--- a/xen/arch/x86/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate.c
@@ -41,3 +41,52 @@
 })
 
 #include "x86_emulate/x86_emulate.c"
+
+/* Called with NULL ctxt in hypercall context. */
+int x86emul_read_dr(unsigned int reg, unsigned long *val,
+                    struct x86_emulate_ctxt *ctxt)
+{
+    struct vcpu *curr = current;
+
+    /* HVM support requires a bit more plumbing before it will work. */
+    ASSERT(is_pv_vcpu(curr));
+
+    switch ( reg )
+    {
+    case 0 ... 3:
+    case 6:
+        *val = curr->arch.debugreg[reg];
+        break;
+
+    case 7:
+        *val = (curr->arch.debugreg[7] |
+                curr->arch.debugreg[5]);
+        break;
+
+    case 4 ... 5:
+        if ( !(curr->arch.pv_vcpu.ctrlreg[4] & X86_CR4_DE) )
+        {
+            *val = curr->arch.debugreg[reg + 2];
+            break;
+        }
+
+        /* Fallthrough */
+    default:
+        if ( ctxt )
+            x86_emul_hw_exception(TRAP_invalid_op, X86_EVENT_NO_EC, ctxt);
+
+        return X86EMUL_EXCEPTION;
+    }
+
+    return X86EMUL_OKAY;
+}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/xen/arch/x86/x86_emulate/x86_emulate.h 
b/xen/arch/x86/x86_emulate/x86_emulate.h
index e5ec8a6122..1c9331c897 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.h
+++ b/xen/arch/x86/x86_emulate/x86_emulate.h
@@ -652,6 +652,9 @@ static inline void x86_emulate_free_state(struct 
x86_emulate_state *state) {}
 void x86_emulate_free_state(struct x86_emulate_state *state);
 #endif
 
+int x86emul_read_dr(unsigned int reg, unsigned long *val,
+                    struct x86_emulate_ctxt *ctxt);
+
 #endif
 
 static inline void x86_emul_hw_exception(
--
generated by git-patchbot for /home/xen/git/xen.git#staging-4.9

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